• Journal of the korean academy of Pediatric Dentistry
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• v.34 no.4
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• pp.551-559
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• 2007

This study was to investigate if cervical vertebrae maturation stages are as useful as hand-wrist maturation stages in evaluating the mandibular growth. The subject consisted of 292 girls aged from 8 to 16 years with normal occlusion. They were classified according to diagnosis by using studycast, lateral cephalogram, and handwrist X-ray film. The results were as follow: 1. Cervical vertebrae and hand-wrist maturation stages increased with age. 2. All mandibular measurements (Ar-Go, Go-Me, N-Go, S-Gn, N-Me) increased linearly with cervical vertebrae maturation stages. 3. Ar-Go, Go-Me, N-Go, S-Gn increased linearly with hand-wrist maturation stages. 4. Ar-Go, Go-Me, N-Go, S-Gn increased relatively rapidly between cervical vertebrae maturation stages 3 and 4. Go-Me and S-Gn increased relatively rapidly between hand-wrist maturation stages 6 and 7. 5. Ar-Go, Go-Me, N-Go, S-Gn, N-Me had high correlations with cervical vertebrae maturation stages as well as hand-wrist maturation stages. These results suggest that cervical vertebrae maturation stages are reliable on evaluating the mandibular growth.

• Membrane Journal
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• v.27 no.1
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• pp.53-59
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• 2017

In this study, the composite membranes prepared by sulfonated graphene oxide (sGO) and Nafion were developed as proton exchange membranes (PEMs) for polymer electrolyte membrane fuel cells (PEMFCs). The sGO/Nafion composite membranes were prepared by mixing Nafion solution with the sGO dispersed in a binary solvent system to improve dispersity of sGO. The composite membranes were investigated in terms of ionic conductivity, ion exchange capacity (IEC), FT-IR, TGA and SEM, etc. As a result, the binary solvent system, i.e., ortho-dichlorobenzene (ODB) and N,N-dimethylacetamide (DMAc), were used to obtain high dispersion of sGO particles in Nafion solution, and the ionic conductivity of the sGO/Nafion composite membrane showed $0.06Scm^{-1}$ similar to other research results at lower water uptake, 11 wt%.

• Journal of the korean academy of Pediatric Dentistry
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• v.39 no.4
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• pp.357-365
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• 2012

There are orthodontic treatment which involves tooth movements and orthopedic treatment which involves skeletal movement. In childhood and adolescence, especially for the treatment of orthopedic treatment, the evaluation of bone maturity and growth potential is very important. The purpose of this study is to assess the developmental stage and to compare the amount of mandibular growth with cephalometric radiographs and hand-wrist radiograph in 6 to 13-year-old children with normal occlusion. The results are as follows : SMI and CVM showed a significant correlation (p < 0.05). Ar-Go, Co-Go, N-Go, S-Gn, N-Me, Co-Gn, Go-Me, Go-Gn increased with increasing maturity of hand-wrist and Ar-Go, Co-Go, N-Go, S-Gn, N-Me, Co-Gn, Go-Me, Go-Gn increased with increasing maturity of cervical vertebrae maturation. Also Ar-Go, Co-Go, N-Go, S-Gn, N-Me, Co-Gn, Go-Me, Go-Gn showed a significant correlation with each of the cervical vertebrae maturation stages and hand-wrist maturation stages (p < 0.05). These results suggested that mandibular growth had a significant correlation with cervical vertebrae maturation stages and hand-wrist maturation stages.

• Applied Chemistry for Engineering
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• v.27 no.1
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• pp.45-49
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• 2016

In the presence of poly(4-styrene sulfonate) (PSS) and excess amount of graphene oxide (GO), we conducted in-situ polymerization of 3,4-ethylenedioxythiophene (EDOT) without an oxidant. XPS and IR spectroscopies of the product (GO-P) showed that PEDOT/PSS was successfully synthesized by oxidative polymerization of EDOT and hybridized with GO. GO-P displayed a stable aqueous suspension, however, the high content (42%) of GO in GO-P diminished electrical conductivity down to $15S{\cdot}m^{-1}$. Annealing of GO-P films at $200^{\circ}C$ for 8 hr induced partial reduction of GO and finally enhanced electrical conductivity up to $212S{\cdot}m^{-1}$.

• Electronic Materials Letters
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• v.14 no.6
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• pp.739-748
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• 2018

ZnS nanowalls, microspheres and rice-shaped nanoparticles have been successfully grown on graphene oxide (GO) sheets by the hydrothermal method. The morphologies, structures, chemical compositions and optical properties of the as-synthesized GO/ZnS have been characterized by X-ray power diffraction, energy dispersive spectrometer, scanning electron microscope, Raman spectra, photoluminescence spectroscopy and ultraviolet-visible absorption spectroscopy. It was found that the concentration of CTAB and the reaction temperature were important in the formation of GO/ZnS microstructures. The photocatalytic activity of the as-synthesized GO/ZnS was investigated through the photocatalytic degradation of textile dyeing waste. Results showed that the catalytic activity of the GO/ZnS porous spheres to methyl orange and methylene blue is higher than those of other samples. The degradation rates of methyl orange and methylene blue by porous spheres in 50 min were 97.6 and 97.1%, respectively. This is mainly attributed to the large specific surface area of GO/ZnS porous spheres and high separation efficiency between photogenerated electron and hole pairs.

• Journal of Environmental Science International
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• v.26 no.1
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• pp.1-10
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• 2017

In this study, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV)/graphene oxide (GO) nanocomposite films containing various content of GO were prepared using solution casting method. The effect of GO content on Young's modulus and dispersion of GO in PHBV matrix was investigated. Also, the thermomechanical properties, oxygen transmission rates and hydrolytic degradation of PHBV/GO nanocomposite films were studied. The addition of GO into PHBV improves the Young's modulus and decreases thermal expansion coefficient. The improvement can be mainly attributed to good dispersion of GO and interfacial interactions between PHBV and GO. Furthermore, PHBV/GO nanocomposite films show good oxygen barrier properties. PHBV/GO nanocomposites show lower hydrolytic degradation rates with increasing content of GO.

• The Korean Journal of Food And Nutrition
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• v.28 no.6
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• pp.1026-1032
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• 2015

This study attempted to find an efficient method for the preparation of high-purity galactooligosaccharides (HP-GOS) using ${\beta}$-galactosidase and yeast fermentation. GOS prepared using Lactozym 3000L showed the greatest enhancement in total GOS of the six ${\beta}$-galatosidases tested. GOS alone achieved 51% conversion of initial lactose. GOS production was enhanced by fermentation with commercial yeast (Saccharomyces cerevisiae); its concentration reached 71% after 36h fermentation with 8% yeast. Component sugar analysis with HPLC indicated that HP-GOS fermented with S. cerevisiae showed significantly increased levels of 4'/6'-galactosyllactose and total GOS as well as a significantly decreased glucose level. HP-GOS facilitated the growth of Lactobacillus sp. (L. acidophilus and L. casei) and Bifidobacterium sp. (B. longum and B. bifidum). In sum, high-purity GOS has been successfully produced through both an enzymatic process and yeast fermentation. GOS encourages the growth of bacteria such as Lactobacillus and Bifidobacterium that may be beneficial to human gastrointestinal health.

• KEPCO Journal on Electric Power and Energy
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• v.2 no.1
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• pp.127-131
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• 2016

Polymer electrolyte membrane for unitized regenerative fuel cells requires high proton conductivity, high dimensional stability, low permeability, and low cost. However, DuPont's Nafion which is a commercial polymer electrolyte membrane has high permeability, high cost, and decreasing proton conductivity and dimensional stability over $80^{\circ}C$. To address these problems, sulfonated poly ether ether ketone (sPEEK) which is a low cost hydrocarbon polymer is selected as matrix polymer for the preparation of polymer electrolyte membrane. In addition, composite membrane with improved proton conductivity and dimensional stability is prepared by introducing sulfonated graphene oxide (sGO). The fundamental properties of polymer electrolyte membranes are analyzed by investigating membrane's water content, dimensional stability, proton conductivity, and morphology. The cell test is conducted to consider the possibility of application of sPEEK/sGO composite membrane for an unitized regenerative fuel cell.

• Clean Technology
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• v.19 no.3
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• pp.300-305
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• 2013

Zinc oxide (ZnO) and reduced graphite oxide (rGO) composites were synthesized and tested as adsorbents for the hydrogen sulfide ($H_2S$) adsorption at mid-to-high (300 to $500^{\circ}C$) temperatures. In order to investigate the critical roles of oxygen containing functional groups, such as hydroxyl, epoxy and carboxyl groups, attached on rGO surface for the $H_2S$ adsorption, various characterization methods (TGA, XRD, FT-IR, SEM and XPS) were conducted. For the reduction process for graphite oxide (GO) to rGO, a microwave irradiation method was used, and it provided a mild reduction environment which can remain substantial amount of oxygen functional groups on rGO surface. Those functional groups were anchoring and holding nano-sized ZnO onto the 2D rGO surface; and it prevented the aggregation effect on the ZnO particles even at high temperature ranges. Therefore, the $H_2S$ adsorption capacity had been increased about 3.5 times than the pure ZnO.

• Membrane Journal
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• v.27 no.3
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• pp.255-262
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• 2017

In this study, systematic integration of graphene oxide (GO) into polyacrylonitrile (PAN) nanofibers was accomplished by electrospinning to examine their mechanical properties. Exfoliated GO was initially prepared by the modified Hummer's method, and the surface of the GO was modified with an organic surfactant (e.g., cetyltrimetylammonium chloride) to improve its stability and dispersity. The overall mechanical property of the nanofiber composite membranes was highly improved. Particularly, the composite membranes with the modified GO exhibited much improved mechanical property, presumably due to the increased stability and dispersity of GO during electrospinning.